What we actually know about the map, written plainly for new people
Everything below is from Rockstar or a sourced interview. Nothing here is inference.
The game is set in the state of Leonida, based on Florida. There are six named regions: Vice City, the Leonida Keys, Grassrivers, Port Gellhorn, Ambrosia, and Mount Kalaga National Park.
Vice City is the main city and contains named districts including Ocean Beach, Little Cuba, the Stockyard, Crosstown and the port. Grassrivers is wetland. Port Gellhorn is a run down coast. Ambrosia is inland industrial and agricultural. Mount Kalaga is northern wilderness on the state border. The Keys are an island chain.
Rockstar have said the whole map is around three times the size of Red Dead Redemption 2's and that Vice City itself is roughly twice the size of Los Santos.
That is genuinely everything. Every layout diagram you have seen is a guess, including the good ones.